Method and apparatus for creating a bi-polar virtual electrode used for the ablation of tissue
Inactive Publication Date: 2004-07-22
MEDTRONIC INC
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Problems solved by technology
The cells then dry up, desiccate, and carbonize, resulting in localized shrinking and an opening in the tissue.
Occasionally, certain heart tissue will misfire, causing the heart to beat irregularly.
One of these disadvantages is that during a procedure, coagulum--dried blood cells and tissue cells--will form on the electrode engaging the tissue.
This is a tedious procedure for the surgeon and the operating staff since it requires the real work of the surgery to be discontinued while the cleaning operation occurs.
Such specialty blades are costly, however.
A second disadvantage of the dry electrode approach is that the electrical heating of the tissue creates smoke that is now known to include cancer-causing agents.
Thus, preferred uses of such equipment will include appropriate ventilation systems, which can themselves become quite elaborate and quite expensive.
A further, and perhaps the most significant, disadvantage of dry electrode electrosurgical tools is revealed during cardiac ablation procedures.
Typically, however, the lesion created by a single insertion is insufficient to cure the irregular heartbeat because the lesion created is of an insufficient size to destroy the errant electrical pathway.
Thus, multiple needle insertions and multiple current applications are almost always required to ablate the errant cardiac pathway, prolonging the surgery and thus increasing the potential risk to the patient.
This foregoing problem is also present in TUNA procedures, which similarly require multiple insertions of the needle electrode into the prostate gland.
Failing to do so will result in the failure to create a lesion of sufficient size otherwise required for a beneficial results.
As with radiofrequency catheter ablation of cardiac tissue, then, the ability to create a lesion of the necessary size to alleviate BPH symptoms is limited and thus requires multiple insertions of the electrode into the prostate.
Additionally, multiple insertions increases the risk of at least one of the placements being in the wrong location and, consequently, the risk that healthy tissue may be undesirably affected while diseased tissue may be left untreated.
First, simply continuing to apply current to the patient with sufficiently increasing voltage to overcome the impedance rises will create a larger lesion, though almost always with undesirable results to the patient.
Method used
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[0028] FIG. 1 illustrates in block form a system 10 for RF ablation useful with the present invention. The system 10 includes a current source of radiofrequency alternating electric current 12, a fluid source of RF ablating fluid 14, including but not limited to saline and other conductive solutions, and a surgical instrument 16 for delivering RF current and ablation fluid to a tissue site (not shown) for ablation purposes. In one preferred embodiment, the surgical instrument 16 is connected to the current source 12 and the fluid source 14. It will be understood that the current source 12 and the fluid source 14 may be combined into a single operational structure controlled by an appropriate microprocessor for a controlled delivery of ablating fluid and a controlled application of RF current, both based upon measured parameters such as but not limited to, flow rate, tissue temperature at the ablation site and at areas surrounding the ablation site, impedance, the rate of change of t...
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A method and apparatus for creating a virtual electrode to ablate bodily tissue. The apparatus includes an outer tube, a first electrode, an inner tube and a second electrode. The outer tube is fluidly connected to a source of conductive fluid and defines a proximal end and a distal end. The distal end includes an opening for delivering conductive fluid from the outer tube. The first electrode is disposed at the distal end of the outer tube for applying a current to conductive fluid delivered from the outer tube. The inner tube is coaxially received within the outer tube and is connected to a source of conductive fluid. The inner tube defines a proximal end and a distal end, with the distal end forming an opening for delivering conductive fluid from the inner tube. Finally, the second electrode is disposed at the distal end of the inner tube for applying a current to conductive fluid delivered from the inner tube. With this configuration, upon final assembly, the distal end of the outer tube is axially spaced from the distal end of the inner tube such that the first electrode is spaced from the second electrode. As a result, a bi-polar virtual electrode can be established.
Description
[0001] This application claims the benefit of U.S. Provisional Application No. 60 / 091,929, filed on Jul. 7, 1998.[0002] The present invention relates generally to an apparatus for creating a virtual electrode. More particularly, the present invention relates to an apparatus for the creation of a virtual electrode that is useful for the ablation of soft tissue and neoplasms.BACKGROUND OF THE PRESENT INVENTION[0003] The utilization of an electric current to produce an ameliorative effect on a bodily tissue has a long history, reportedly extending back to the ancient Greeks. The effects on bodily tissue from an applied electric current, and thus the dividing line between harmful and curative effects, will vary depending upon the voltage levels, current levels, the length of time the current is applied, and the tissue involved. One such effect resulting from the passage of an electric current through tissue is heat generation.[0004] Body tissue, like all non-superconducting materials, c...
Claims
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Login to View More IPC IPC(8): A61B18/00A61B18/14
CPCA61B18/14A61B18/1482A61B2018/00005A61B2018/00053A61B2018/00291A61B2018/00642A61B2218/007A61B2018/00791A61B2018/00875A61B2018/126A61B2018/1472A61B2218/002A61B2018/00702
InventorMULIER, PETER M. J.HOEY, MICHAEL F.
OwnerMEDTRONIC INC